Validation By Control ASP.Net

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  4. Validate asp dropdownlist in VB net
<%@ Page Language="VB" %>

    Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs)
        If Page.IsValid Then
            lblResult.Text = dropFavoriteColor.SelectedValue
        End If
    End Sub



    Show Initial Value


    
    

    
            id="lblFavoriteColor"
        Text="Favorite Color:"
        AssociatedControlID="dropFavoriteColor"
        Runat="server" />
    
            id="dropFavoriteColor"
        Runat="server">
        
            
            
            
    
            id="reqFavoriteColor"
        Text="(Required)"
        InitialValue="none"
        ControlToValidate="dropFavoriteColor"
        Runat="server" />
        
    
    
            id="btnSubmit"
        Text="Submit"
        Runat="server" OnClick="btnSubmit_Click" />
    
    
    
            id="lblResult"
        Runat="server" />